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          LV06-02-内核模块-06-printk
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<details class="folding-tag" blue><summary> 点击查看使用工具及版本 </summary>
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              <table>    <tr>        <td align="center" rowspan="5">PC端开发环境</td>        <td align="center" width=150px>Windows</td>        <td align="left">Windows11</td>    </tr>    <tr>        <td align="center">Ubuntu</td>        <td align="left">Ubuntu20.04.2的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 17 Pro</td>        <td align="left">17.6.0 build-24238078</td>      </tr>    <tr>        <td align="center">终端软件</td>        <td align="left">MobaXterm(Professional Edition v23.0 Build 5042 (license))</td>    </tr>    <tr>        <td align="center">Win32DiskImager</td>        <td align="left">Win32DiskImager v1.0</td>      </tr>    <tr>        <td align="center" rowspan="3">Linux开发板环境</td>        <td align="center">Linux开发板</td>        <td align="left">正点原子 i.MX6ULL Linux 阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，使用的uboot版本为U-Boot 2019.04</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.19.71(NXP官方提供)</td>      </tr></table>
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<details class="folding-tag" blue><summary> 点击查看本文参考资料 </summary>
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              <table>    <tr>        <td align="center">分类</td>        <td align="center">网址</td>        <td align="center">说明</td>    </tr>    <tr>        <td align="center" rowspan="5">官方网站</td>        <td align="left"><a href="https://www.arm.com/" target="_blank">https://www.arm.com/</a></td>        <td align="left">ARM官方网站，在这里我们可以找到Cotex-Mx以及ARMVx的一些文档</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxp.com.cn/" target="_blank">https://www.nxp.com.cn/ </a></td>        <td align="left">NXP官方网站</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxpic.org.cn/" target="_blank">https://www.nxpic.org.cn/</a></td><td align="left">NXP 官方社区</td>    </tr>    <tr>        <td align="left"><a href="https://u-boot.readthedocs.io/en/latest/" target="_blank">https://u-boot.readthedocs.io/en/latest/</a></td><td align="left">u-boot官网</td>    </tr>    <tr>        <td align="left"><a href="https://www.kernel.org/" target="_blank">https://www.kernel.org/</a></td><td align="left">linux内核官网</td>    </tr></table>
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            </details>

<details class="folding-tag" blue><summary> 点击查看相关文件下载 </summary>
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              <table>    <tr>        <td align="center">分类</td>        <td align="center">网址</td>        <td align="center">说明</td>    </tr>    <tr>        <td align="center" rowspan="3">NXP</td>        <td align="left"><a href="https://github.com/nxp-imx" target="_blank">https://github.com/nxp-imx</a></td>        <td align="left">NXP imx开发资源GitHub组织，里边会有u-boot和linux内核的仓库</td>    </tr>    <tr>        <td align="left"><a href="https://github.com/nxp-imx/linux-imx/releases/tag/v4.19.71" target="_blank">nxp-imx/linux-imx/releases/tag/v4.19.71</a></td>        <td align="left">NXP linux内核仓库tags中的v4.19.71</td>    </tr>    <tr>        <td align="left"><a href="https://github.com/nxp-imx/uboot-imx/releases/tag/rel_imx_4.19.35_1.1.0" target="_blank">nxp-imx/uboot-imx/releases/tag/rel_imx_4.19.35_1.1.0</a></td>        <td align="left">NXP u-boot仓库tags中的rel_imx_4.19.35_1.1.0</td>    </tr>    <tr>        <td align="center" rowspan="2">I.MX6ULL</td>        <td align="left"><a href="https://www.nxp.com.cn/docs/en/data-sheet/IMX6ULLIEC.pdf" target="_blank">i.MX 6ULL Applications Processors for Industrial Products</a></td>        <td align="left">I.MX6ULL 芯片手册（datasheet，可以在线查看）</td>    </tr>    <tr>        <td align="left"><a href="https://www.nxp.com.cn/webapp/Download?colCode=IMX6ULLRM&lang_cd=zh" target="_blank">i.MX 6ULL Applications ProcessorReference Manual</a></td>        <td align="left">I.MX6ULL 参考手册（下载后才能查看，需要登录NXP官网）</td>    </tr>    <tr>        <td align="center" rowspan="2">Source Code</td>        <td align="left"><a href="https://elixir.bootlin.com/linux/latest/source" target="_blank">https://elixir.bootlin.com/linux/latest/source</a></td>        <td align="left">linux kernel源码</td>    </tr>    <tr>        <td align="left"><a href="https://elixir.bootlin.com/u-boot/latest/source" target="_blank">https://elixir.bootlin.com/u-boot/latest/source</a></td>        <td align="left">uboot源码</td>    </tr></table>
              </div>
            </details>

<h1 id="一、概述"><a href="#一、概述" class="headerlink" title="一、概述"></a><font size=3>一、概述</font></h1><p>大部分常用的C库函数在Linux内核中都已经得到了实现。在所有没有实现的函数中，最著名的就数printf()函数了。内核代码虽然无法调用 printf()函数，但它可以调用printk()函数。printk()函数负责把格式化好的字符串拷贝到内核日志缓冲上，这样syslog程序就可 以通过读取该缓冲区来获取内核信息。</p>
<p>printk()函数是直接使用了向终端写函数tty_write()。而printf()函数是调用write()系统调用函数向标准输出设备写。所以 在用户态（如进程0）不能够直接使用printk()函数，而在内核态由于他已是特权级，所以无需系统调用来改变特权级，因而能够直接使用 printk()函数。printf是使用了标准的C库函数的时候才能使用的，而<strong>内核中无法使用标准的C库函数</strong>，所以就连最常见的printf都不能使用。</p>
<h1 id="二、两个级别"><a href="#二、两个级别" class="headerlink" title="二、两个级别"></a><font size=3>二、两个级别</font></h1><h2 id="1-日志级别"><a href="#1-日志级别" class="headerlink" title="1. 日志级别"></a><font size=3>1. 日志级别</font></h2><h3 id="1-1-有哪些？"><a href="#1-1-有哪些？" class="headerlink" title="1.1 有哪些？"></a><font size=3>1.1 有哪些？</font></h3><p>printk相比printf来说还多了个日志级别的设置，用来控制printk打印的这条信息是否在终端上显示的，当<strong>日志级别</strong>的数值小于<strong>控制台级别</strong>时，printk要打印的信息才会在控制台打印出来，否则不会显示在控制台。在我们内核中一共有8种级别（数字越小级别越高），他们定义在 <a target="_blank" rel="noopener" href="https://elixir.bootlin.com/linux/v4.19.71/source/include/linux/kern_levels.h#L8">kern_levels.h - include&#x2F;linux&#x2F;kern_levels.h</a> 中，分别为：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_EMERG      KERN_SOH <span class="string">&quot;0&quot;</span>    <span class="comment">/* system is unusable */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_ALERT      KERN_SOH <span class="string">&quot;1&quot;</span>    <span class="comment">/* action must be taken immediately */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_CRIT       KERN_SOH <span class="string">&quot;2&quot;</span>    <span class="comment">/* critical conditions */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_ERR        KERN_SOH <span class="string">&quot;3&quot;</span>    <span class="comment">/* error conditions */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_WARNING    KERN_SOH <span class="string">&quot;4&quot;</span>    <span class="comment">/* warning conditions */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_NOTICE     KERN_SOH <span class="string">&quot;5&quot;</span>    <span class="comment">/* normal but significant condition */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_INFO       KERN_SOH <span class="string">&quot;6&quot;</span>    <span class="comment">/* informational */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> KERN_DEBUG      KERN_SOH <span class="string">&quot;7&quot;</span>    <span class="comment">/* debug-level messages */</span></span></span><br></pre></td></tr></table></figure>

<p>所有的<a target="_blank" rel="noopener" href="https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.printk"><code>printk()</code></a>消息都会被打印到内核日志缓冲区，这是一个通过&#x2F;dev&#x2F;kmsg输出到用户空间的环 形缓冲区。读取它的通常方法是使用 <code>dmesg</code> 。日志级别指定了一条消息的重要性。内核根据日志级别和当前 console_loglevel （一个内核变量）决定是否立即显示消息（将其打印到当前控制台）。如果消息的优先级比 console_loglevel 高（日志级 别值较低），消息将被打印到控制台。如果省略了日志级别，则以 <code>KERN_DEFAULT</code> 级别打印消息。格式字符串虽然与C99基本兼容，但并不遵循完全相同的规范。它有一些扩展和一些限制（没 有 <code>%n</code> 或浮点转换指定符）。</p>
<h3 id="1-2-怎么控制？"><a href="#1-2-怎么控制？" class="headerlink" title="1.2 怎么控制？"></a><font size=3>1.2 怎么控制？</font></h3><p>我们可以直接在printk中指定本条打印信息的级别，一般格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">printk(KERN_INFO <span class="string">&quot;Message: %s\n&quot;</span>, arg);</span><br></pre></td></tr></table></figure>

<p>直接在格式字符串前指定打印等级即可。</p>
<h2 id="2-控制台级别"><a href="#2-控制台级别" class="headerlink" title="2. 控制台级别"></a><font size=3>2. 控制台级别</font></h2><h3 id="2-1-有哪些？"><a href="#2-1-有哪些？" class="headerlink" title="2.1 有哪些？"></a><font size=3>2.1 有哪些？</font></h3><p>上边提到了控制台级别，控制台级别定义在哪？它们定义在 <a target="_blank" rel="noopener" href="https://elixir.bootlin.com/linux/v4.19.71/source/include/linux/printk.h#L51">printk.h - include&#x2F;linux&#x2F;printk.h</a> 文件中：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* printk&#x27;s without a loglevel use this.. */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* We show everything that is MORE important than this.. */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_SILENT  0 <span class="comment">/* Mum&#x27;s the word */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_MIN     1 <span class="comment">/* Minimum loglevel we let people use */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_QUIET   4 <span class="comment">/* Shhh ..., when booted with &quot;quiet&quot; */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_DEFAULT 7 <span class="comment">/* anything MORE serious than KERN_DEBUG */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_DEBUG  10 <span class="comment">/* issue debug messages */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> CONSOLE_LOGLEVEL_MOTORMOUTH 15  <span class="comment">/* You can&#x27;t shut this one up */</span></span></span><br><span class="line"></span><br><span class="line"><span class="keyword">extern</span> <span class="type">int</span> console_printk[];</span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> console_loglevel (console_printk[0])</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> default_message_loglevel (console_printk[1])</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> minimum_console_loglevel (console_printk[2])</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> default_console_loglevel (console_printk[3])</span></span><br></pre></td></tr></table></figure>

<p>我们看一下console_printk这个数组（定义在<a target="_blank" rel="noopener" href="https://elixir.bootlin.com/linux/v4.19.71/source/kernel/printk/printk.c#L61">printk.c - kernel&#x2F;printk&#x2F;printk.c</a>中）：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> console_printk[<span class="number">4</span>] = &#123;</span><br><span class="line">        CONSOLE_LOGLEVEL_DEFAULT,       <span class="comment">/* console_loglevel */</span></span><br><span class="line">        MESSAGE_LOGLEVEL_DEFAULT,       <span class="comment">/* default_message_loglevel */</span></span><br><span class="line">        CONSOLE_LOGLEVEL_MIN,           <span class="comment">/* minimum_console_loglevel */</span></span><br><span class="line">        CONSOLE_LOGLEVEL_DEFAULT,       <span class="comment">/* default_console_loglevel */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<ul>
<li>console_printk[0]：<code>CONSOLE_LOGLEVEL_DEFAULT</code>，控制台日志级别，优先级高于该值的消息将在控制台显示（也就是终端）。</li>
<li>console_printk[1]：<code>MESSAGE_LOGLEVEL_DEFAULT</code>，默认消息日志级别，printk没定义优先级时，打印这个优先级以上的消息。</li>
<li>console_printk[2]：<code>CONSOLE_LOGLEVEL_MIN</code>，最小控制台日志级别，控制台日志级别可被设置的最小值（最高优先级</li>
<li>console_printk[3]：<code>CONSOLE_LOGLEVEL_DEFAULT</code>，默认的控制台日志级别。</li>
</ul>
<p>我们可以在linux系统中通过以下命令查看：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">cat /proc/sys/kernel/printk</span><br></pre></td></tr></table></figure>

<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%86%85%E6%A0%B8%E6%A8%A1%E5%9D%97-06-printk/img/image-20241120231849696.png" alt="image-20241120231849696" />

<p>如上图，从左到右依次对应当前控制台日志级别、默认消息日志级别、 最小的控制台级别、默认控制台日志级别。</p>
<ul>
<li>console_printk[0]：为<code>CONSOLE_LOGLEVEL_DEFAULT</code>：默认为7，所有优先级高于7的log等级（0~6），都会打印在终端上。</li>
<li>console_printk[1]：为<code>MESSAGE_LOGLEVEL_DEFAULT</code>：默认为4，printk打印消息时的默认等级。</li>
<li>console_printk[2]：为<code>CONSOLE_LOGLEVEL_MIN</code>：控制台日志级别可被设置的最小值（最高优先级），这里默认为1。</li>
<li>console_printk[3]：为<code>CONSOLE_LOGLEVEL_DEFAULT</code>：默认的控制台日志级别，默认为7。</li>
</ul>
<blockquote>
<p>打印内核所有打印信息：dmesg，注意内核log缓冲区大小有限制，缓冲区数据可能被覆盖掉。</p>
</blockquote>
<h3 id="2-2-怎么控制？"><a href="#2-2-怎么控制？" class="headerlink" title="2.2 怎么控制？"></a><font size=3>2.2 怎么控制？</font></h3><p>我们直接在终端输入以下指令即可：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">echo 8 4 1 7 &gt; /proc/sys/kernel/printk</span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">也可以用下边的命令</span></span><br><span class="line">dmesg -n 5 # 这种只能修改 控制台日志级别 也就是 console_printk[0]</span><br></pre></td></tr></table></figure>

<p>中间的数字分别就代表各个等级，可以直接这样修改。例如：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/02IMX6ULL%E5%B9%B3%E5%8F%B0/LV06-%E9%A9%B1%E5%8A%A8%E5%BC%80%E5%8F%91/LV06-02-%E5%86%85%E6%A0%B8%E6%A8%A1%E5%9D%97-06-printk/img/image-20241120231958158.png" alt="image-20241120231958158" />

<h1 id="三、使用实例"><a href="#三、使用实例" class="headerlink" title="三、使用实例"></a><font size=3>三、使用实例</font></h1><h2 id="1-打印等级实例"><a href="#1-打印等级实例" class="headerlink" title="1. 打印等级实例"></a><font size=3>1. 打印等级实例</font></h2><p>代码可以看这里：<a target="_blank" rel="noopener" href="https://gitee.com/sumumm/imx6ull-linuxdriver-eg/tree/master/01_module_load/printk_eg">01_module_load&#x2F;printk_eg · sumumm&#x2F;imx6ull-linuxdriver-eg - 码云 - 开源中国 (gitee.com)</a>。操作的时候主要是看加载驱动的时候的打印信息，主要是以下信息：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">printk(KERN_EMERG<span class="string">&quot;KERN_EMERG:%s\r\n&quot;</span>, KERN_EMERG);</span><br><span class="line">printk(KERN_ALERT<span class="string">&quot;KERN_ALERT:%s\r\n&quot;</span>, KERN_ALERT);</span><br><span class="line">printk(KERN_CRIT<span class="string">&quot;KERN_CRIT:%s\r\n&quot;</span>, KERN_CRIT);</span><br><span class="line">printk(KERN_ERR<span class="string">&quot;KERN_ERR:%s\r\n&quot;</span>, KERN_ERR);</span><br><span class="line">printk(KERN_WARNING<span class="string">&quot;KERN_WARNING:%s\r\n&quot;</span>, KERN_WARNING);</span><br><span class="line">printk(KERN_NOTICE<span class="string">&quot;KERN_NOTICE:%s\r\n&quot;</span>, KERN_NOTICE);</span><br><span class="line">printk(KERN_INFO<span class="string">&quot;KERN_INFO:%s\r\n&quot;</span>, KERN_INFO);</span><br><span class="line">printk(KERN_DEBUG<span class="string">&quot;KERN_DEBUG:%s\r\n&quot;</span>, KERN_DEBUG);</span><br></pre></td></tr></table></figure>

<p>然后通过下边的命令修改各个默认值来看内核日志打印情况：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">echo 8 4 1 7 &gt; /proc/sys/kernel/printk</span><br><span class="line">echo 0 4 1 7 &gt; /proc/sys/kernel/printk</span><br></pre></td></tr></table></figure>

<h2 id="2-打印出git版本和编译时间"><a href="#2-打印出git版本和编译时间" class="headerlink" title="2. 打印出git版本和编译时间"></a><font size=3>2. 打印出git版本和编译时间</font></h2><p>在内核模块中不支持<code>__DATE__</code>选项，另外对于内核源码外编译的内核模块而言，我们不是很容易在执行make的时候为编译器添加-D选项，至少我在学习到这里的时候没有发现什么好办法，然后我去参考了uboot，发现uboot是生成了两个<code>.h</code>头文件，于是仿照它来进行，具体的实现过程可以看这里：<a href="https://sumumm.github.io/post/f68c951e.html#more">LV05-02-U-Boot-07-uboot编译时间与版本 | 苏木</a></p>
<p>使用实例可以看这里：<a target="_blank" rel="noopener" href="https://gitee.com/sumumm/imx6ull-driver-demo/tree/master/03_module_basic/03_printk_prj_info">imx6ull-driver-demo: i.mx6ull驱动开发demo - Gitee.com</a>。实现makefile后，我们就可以包含对应的头文件，打印编译时间和git版本信息了。</p>
<h3 id="2-1-makefile文件"><a href="#2-1-makefile文件" class="headerlink" title="2.1 makefile文件"></a><font size=3>2.1 makefile文件</font></h3><figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br><span class="line">95</span><br><span class="line">96</span><br><span class="line">97</span><br><span class="line">98</span><br><span class="line">99</span><br><span class="line">100</span><br><span class="line">101</span><br><span class="line">102</span><br><span class="line">103</span><br><span class="line">104</span><br><span class="line">105</span><br><span class="line">106</span><br><span class="line">107</span><br><span class="line">108</span><br><span class="line">109</span><br><span class="line">110</span><br><span class="line">111</span><br><span class="line">112</span><br><span class="line">113</span><br><span class="line">114</span><br><span class="line">115</span><br><span class="line">116</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment"># 模块名和模块测试APP名称</span></span><br><span class="line">MODULE_NAME       := printk_prj_info</span><br><span class="line"></span><br><span class="line">ARCH              ?= arm</span><br><span class="line">MAKE_PARAM        :=</span><br><span class="line">CURRENT_PATH      := <span class="variable">$(<span class="built_in">shell</span> pwd)</span></span><br><span class="line">KERNEL_KO_RELEASE  = <span class="variable">$(<span class="built_in">shell</span> git rev-parse --verify --short HEAD)</span></span><br><span class="line"><span class="keyword">ifeq</span> (<span class="string">&quot;$(origin V)&quot;</span>, <span class="string">&quot;command line&quot;</span>)</span><br><span class="line">  KBUILD_VERBOSE = <span class="variable">$(V)</span></span><br><span class="line"><span class="keyword">endif</span></span><br><span class="line"><span class="keyword">ifndef</span> KBUILD_VERBOSE</span><br><span class="line">  KBUILD_VERBOSE = 0</span><br><span class="line"><span class="keyword">endif</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">ifeq</span> (<span class="variable">$(KBUILD_VERBOSE)</span>,1)</span><br><span class="line">  quiet =</span><br><span class="line">  Q =</span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">  quiet=quiet_</span><br><span class="line">  Q = @</span><br><span class="line"><span class="keyword">endif</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#=====================================================</span></span><br><span class="line">INCDIRS 		  := ./ 			   </span><br><span class="line">SRCDIRS			  := ./</span><br><span class="line"></span><br><span class="line">INCLUDE			  := <span class="variable">$(<span class="built_in">patsubst</span> %, -I %, <span class="variable">$(INCDIRS)</span>)</span></span><br><span class="line"><span class="comment">#=====================================================</span></span><br><span class="line"><span class="comment"># NFS 共享目录</span></span><br><span class="line">TFTP_SERVER       ?= ~/3tftp</span><br><span class="line">NFS_SERVER        ?= ~/4nfs</span><br><span class="line"></span><br><span class="line">TFTP_DIR          ?= <span class="variable">$(TFTP_SERVER)</span></span><br><span class="line">ROOTFS_ROOT_DIR   ?= <span class="variable">$(NFS_SERVER)</span>/imx6ull_rootfs</span><br><span class="line"><span class="comment">#ROOTFS_MODULE_DIR ?= $(ROOTFS_ROOT_DIR)/lib/modules/4.19.71-00007-g51f3cd8ec-dirty</span></span><br><span class="line">ROOTFS_MODULE_DIR ?= <span class="variable">$(ROOTFS_ROOT_DIR)</span>/drivers_demo</span><br><span class="line"><span class="comment">#=====================================================</span></span><br><span class="line"><span class="keyword">ifeq</span> (<span class="variable">$(KERNELRELEASE)</span>,)</span><br><span class="line"></span><br><span class="line"><span class="comment"># 选择可执行文件运行的平台</span></span><br><span class="line"><span class="keyword">ifeq</span> (<span class="variable">$(ARCH)</span>, arm)</span><br><span class="line">KERNELDIR            ?= ~/7Linux/imx6ull-kernel </span><br><span class="line">MAKE_PARAM           += ARCH=arm</span><br><span class="line">MAKE_PARAM           += CROSS_COMPILE=arm-linux-gnueabihf-</span><br><span class="line">CROSS_COMPILE_PREFIX ?= arm-linux-gnueabihf-</span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">KERNELDIR            ?= /lib/modules/<span class="variable">$(<span class="built_in">shell</span> uname -r)</span>/build</span><br><span class="line">CROSS_COMPILE_PREFIX ?=</span><br><span class="line"><span class="keyword">endif</span></span><br><span class="line"></span><br><span class="line">CC                   := <span class="variable">$(CROSS_COMPILE_PREFIX)</span>gcc</span><br><span class="line">LD                   := <span class="variable">$(CROSS_COMPILE_PREFIX)</span>ld</span><br><span class="line"></span><br><span class="line"><span class="keyword">include</span> Kbuild.<span class="keyword">include</span></span><br><span class="line"></span><br><span class="line">srctree              := .</span><br><span class="line">timestamp_h          := timestamp_autogenerated.h</span><br><span class="line">version_h            := version_autogenerated.h</span><br><span class="line"></span><br><span class="line"><span class="keyword">export</span> CC LD srctree</span><br><span class="line"></span><br><span class="line"><span class="comment"># 编译模块和测试程序</span></span><br><span class="line"><span class="section">all: <span class="variable">$(timestamp_h)</span> <span class="variable">$(version_h)</span> modules</span></span><br><span class="line"></span><br><span class="line"><span class="section">modules:</span></span><br><span class="line">	<span class="variable">$(MAKE)</span> <span class="variable">$(MAKE_PARAM)</span> -C <span class="variable">$(KERNELDIR)</span> M=<span class="variable">$(CURRENT_PATH)</span> modules <span class="variable">$(INCLUDE)</span></span><br><span class="line"></span><br><span class="line"><span class="section">modules_install:</span></span><br><span class="line">	<span class="variable">$(MAKE)</span> <span class="variable">$(MAKE_PARAM)</span> -C <span class="variable">$(KERNELDIR)</span> M=<span class="variable">$(CURRENT_PATH)</span> modules INSTALL_MOD_PATH=<span class="variable">$(ROOTFS_MODULE_DIR)</span> modules_install</span><br><span class="line"></span><br><span class="line"><span class="variable">$(timestamp_h)</span>: <span class="variable">$(srctree)</span>/Makefile FORCE</span><br><span class="line">	<span class="variable">$(<span class="built_in">call</span> filechk,timestamp_autogenerated.h)</span></span><br><span class="line">	</span><br><span class="line"><span class="variable">$(version_h)</span>: <span class="variable">$(srctree)</span>/Makefile FORCE</span><br><span class="line">	<span class="variable">$(<span class="built_in">call</span> filechk,version_autogenerated.h)</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># 拷贝相关文件到nfs共享目录</span></span><br><span class="line"><span class="section">install:</span></span><br><span class="line">	@sudo cp -v <span class="variable">$(MODULE_NAME)</span>.ko <span class="variable">$(ROOTFS_MODULE_DIR)</span></span><br><span class="line"></span><br><span class="line"><span class="section">uninstall:</span></span><br><span class="line">	@sudo rm -vf <span class="variable">$(ROOTFS_MODULE_DIR)</span>/<span class="variable">$(MODULE_NAME)</span>.ko </span><br><span class="line"></span><br><span class="line">PHONY += FORCE</span><br><span class="line"><span class="section">FORCE:</span></span><br><span class="line"></span><br><span class="line">PHONY += clean</span><br><span class="line"><span class="section">clean:</span></span><br><span class="line">	rm -rf *.o *.ko *.o.d</span><br><span class="line">	rm -rf .*.cmd  *.mod.* *.mod modules.order Module.symvers .tmp_versions .cache.mk </span><br><span class="line">	rm -rf <span class="variable">$(timestamp_h)</span></span><br><span class="line">	rm -rf <span class="variable">$(version_h)</span></span><br><span class="line"></span><br><span class="line"><span class="meta"><span class="keyword">.PHONY</span>: $(PHONY)</span></span><br><span class="line"></span><br><span class="line"><span class="section">help:</span></span><br><span class="line">	@echo <span class="string">&quot;\033[1;32m================================ Help ================================\033[0m&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;Ubuntu may need to add sudo:&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;insmod &lt;module_name&gt;.ko   # Load module&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;rmmod &lt;module_name&gt;       # Uninstall the module&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;dmesg -C                  # Clear the kernel print information&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;lsmod                     # Check the kernel modules that have been inserted&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;dmesg                     # View information printed by the kernel&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;file &lt;module_name&gt;.ko     # View \&quot;.Ko\&quot; file information&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;make ARCH=x86_64          # x86_64 platform&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;make                      # arm platform&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;\033[1;32m======================================================================\033[0m&quot;</span></span><br><span class="line"></span><br><span class="line"><span class="section">print:</span></span><br><span class="line">	@echo <span class="string">&quot;KERNELDIR = <span class="variable">$(KERNELDIR)</span>&quot;</span></span><br><span class="line">	@echo <span class="string">&quot;INCLUDE   = <span class="variable">$(INCLUDE)</span>&quot;</span></span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">CONFIG_MODULE_SIG = n</span><br><span class="line">obj-m            += <span class="variable">$(MODULE_NAME)</span>.o</span><br><span class="line"><span class="keyword">endif</span></span><br></pre></td></tr></table></figure>

<h3 id="2-2-Kbuild-include"><a href="#2-2-Kbuild-include" class="headerlink" title="2.2 Kbuild.include"></a><font size=3>2.2 Kbuild.include</font></h3><figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">define</span> filechk_timestamp_autogenerated.h</span><br><span class="line">	(if test -n <span class="string">&quot;$$&#123;SOURCE_DATE_EPOCH&#125;&quot;</span>; then \</span><br><span class="line">		SOURCE_DATE=<span class="string">&quot;@$$&#123;SOURCE_DATE_EPOCH&#125;&quot;</span>; \</span><br><span class="line">		DATE=<span class="string">&quot;&quot;</span>; \</span><br><span class="line">		for date in gdate date.gnu date; do \</span><br><span class="line">			$$&#123;date&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> &gt;/dev/null 2&gt;&amp;1 &amp;&amp; DATE=<span class="string">&quot;$$&#123;date&#125;&quot;</span>; \</span><br><span class="line">		done; \</span><br><span class="line">		if test -n <span class="string">&quot;$$&#123;DATE&#125;&quot;</span>; then \</span><br><span class="line">			LC_ALL=C $$&#123;DATE&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> +&#x27;<span class="comment">#define KERNEL_KO_DATE &quot;%b %d %C%y&quot;&#x27;; \</span></span><br><span class="line">			LC_ALL=C $$&#123;DATE&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> +&#x27;<span class="comment">#define KERNEL_KO_TIME &quot;%T&quot;&#x27;; \</span></span><br><span class="line">			LC_ALL=C $$&#123;DATE&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> +&#x27;<span class="comment">#define KERNEL_KO_TZ &quot;%z&quot;&#x27;; \</span></span><br><span class="line">			LC_ALL=C $$&#123;DATE&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> +&#x27;<span class="comment">#define KERNEL_KO_DMI_DATE &quot;%m/%d/%Y&quot;&#x27;; \</span></span><br><span class="line">			LC_ALL=C $$&#123;DATE&#125; -u -d <span class="string">&quot;$$&#123;SOURCE_DATE&#125;&quot;</span> +&#x27;<span class="comment">#define KERNEL_KO_BUILD_DATE 0x%Y%m%d&#x27;; \</span></span><br><span class="line">		<span class="keyword">else</span> \</span><br><span class="line">			return 42; \</span><br><span class="line">		fi; \</span><br><span class="line">	<span class="keyword">else</span> \</span><br><span class="line">		LC_ALL=C date +&#x27;<span class="comment">#define KERNEL_KO_DATE &quot;%b %d %C%y&quot;&#x27;; \</span></span><br><span class="line">		LC_ALL=C date +&#x27;<span class="comment">#define KERNEL_KO_TIME &quot;%T&quot;&#x27;; \</span></span><br><span class="line">		LC_ALL=C date +&#x27;<span class="comment">#define KERNEL_KO_TZ &quot;%z&quot;&#x27;; \</span></span><br><span class="line">		LC_ALL=C date +&#x27;<span class="comment">#define KERNEL_KO_DMI_DATE &quot;%m/%d/%Y&quot;&#x27;; \</span></span><br><span class="line">		LC_ALL=C date +&#x27;<span class="comment">#define KERNEL_KO_BUILD_DATE 0x%Y%m%d&#x27;; \</span></span><br><span class="line">	fi)</span><br><span class="line"><span class="keyword">endef</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">define</span> filechk_version_autogenerated.h</span><br><span class="line">	(echo \<span class="comment">#define PLAIN_VERSION \&quot;$(KERNEL_KO_RELEASE)\&quot;; \</span></span><br><span class="line">	echo \<span class="comment">#define KERNEL_KO_VERSION \&quot;\&quot; PLAIN_VERSION; \</span></span><br><span class="line">	echo \<span class="comment">#define CC_VERSION_STRING \&quot;$$(LC_ALL=C $(CC) --version | head -n 1)\&quot;; \</span></span><br><span class="line">	echo \<span class="comment">#define LD_VERSION_STRING \&quot;$$(LC_ALL=C $(LD) --version | head -n 1)\&quot;; )</span></span><br><span class="line"><span class="keyword">endef</span></span><br><span class="line"></span><br><span class="line"><span class="keyword">define</span> filechk</span><br><span class="line">	<span class="variable">$(Q)</span>set -e;				\</span><br><span class="line">	: &#x27;  CHK     <span class="variable">$@</span>&#x27;;		\</span><br><span class="line">	mkdir -p <span class="variable">$(<span class="built_in">dir</span> <span class="variable">$@</span>)</span>;			\</span><br><span class="line">	$(filechk_$(1)) &lt; <span class="variable">$&lt;</span> &gt; <span class="variable">$@</span>.tmp;		\</span><br><span class="line">	if [ -r <span class="variable">$@</span> ] &amp;&amp; cmp -s <span class="variable">$@</span> <span class="variable">$@</span>.tmp; then	\</span><br><span class="line">		rm -f <span class="variable">$@</span>.tmp;			\</span><br><span class="line">	<span class="keyword">else</span>					\</span><br><span class="line">		: &#x27;  UPD     <span class="variable">$@</span>&#x27;;	\</span><br><span class="line">		mv -f <span class="variable">$@</span>.tmp <span class="variable">$@</span>;		\</span><br><span class="line">	fi</span><br><span class="line"><span class="keyword">endef</span></span><br></pre></td></tr></table></figure>


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    <p><span>文章标题:</span><a href="/post/fcdda906.html">LV06-02-内核模块-06-printk</a></p>
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